Need a few ideas. 2003, 2500HD, Duramax, Allison. I just installed a 14 bolt 10.5 w/3.21 gears[stock GM limited slip] and the full transgo kit at the same time. I cleared codes and set the tire dia[compensate for the gears] with a Hypertech ACCUPRO. I now have two issues. FIRST, when cold the trans down shifts hard into first gear when slowing. Once warmed up the down shift is not abrupt.
SECOND, when backing up a sloped drive or in loose gravel, the trans will kick out of reverse, then in, then out until I stop. It does this quite hard. Scares the (*&^ out of my lady friend[her drive].
Any ideas would be appreciated. Chris

Any codes? How much have you driven it since installing the kit? Did you reinstall the range switch in the same position, or did you fight the connectors and damage a pin?

There was one code B1045.